How to compress a photo to 100 KB for an online form

To get a photo under 100 KB, open the image compressor, type a number just under the limit in Max size (KB) and download the result. It lowers the quality, and then the dimensions, until the file fits, all inside your browser. For a photo of a document, first limit the width to about 1,300 pixels so the text stays sharp, and if it's an iPhone HEIC photo, convert it to JPG first.

Why the form rejects your photo

Many job portals, university applications and government procedures only accept files up to 100, 200 or 500 KB, and often only JPG, PNG or PDF. A photo straight from your phone is far over that, so the upload fails with a message like "file too large" or "invalid format".

Before you start, read what the form asks for. The limit is usually written next to the upload button or in the error message. Look for three things: the maximum size in KB, the formats it accepts, and sometimes exact dimensions in pixels, which is common for ID-style photos.

Why a phone photo weighs 3 to 5 MB

A phone camera takes photos of 12 megapixels or more: about 4,000 by 3,000 tiny dots of color, called pixels. It saves them at high quality so no detail is lost, including the grain in dark areas, which is hard to compress. The result is usually several megabytes, often 3 to 5 MB. A 100 KB limit is about a fortieth of a 4 MB photo.

Three things decide how much an image weighs:

What	What it means	Effect
Dimensions	Width × height in pixels	The biggest lever. Half the width and half the height leaves a quarter of the pixels and a file several times smaller.
Quality	How much fine detail a JPEG keeps, from 1 to 100	Lower quality means a smaller file. Around 70 to 80 usually looks like the original; very low values blur edges and letters.
Format	JPEG, PNG, WebP, HEIC	JPEG is small for photos and accepted everywhere. PNG keeps every pixel exactly, so photos in PNG are heavy. WebP and HEIC are efficient but many forms reject them.

The person reviewing your application sees it on a screen, which can't show 12 million pixels at once anyway, so a well-sized copy looks the same to them.

Step by step with the image compressor

1. Open the image compressor and drop your photo, or tap to choose it. You can add several at once. Everything happens on your device: the photos are never uploaded.
2. In Max size (KB), type a little less than the limit, such as 95 for a 100 KB limit or 190 for 200 KB. The tool counts 1 KB as 1,024 bytes, and some websites count 1,000, so the small margin avoids a surprise rejection.
3. Leave Format on Auto, which saves photos as JPEG. If your image has a transparent background, such as a signature cut out on a PNG, Auto saves it as WebP. Many forms don't accept WebP, so choose JPEG instead.
4. For a document, type about 1,300 in Max width (or in Max height if the photo is sideways). With a max size set, the tool lowers the quality first and only reduces the dimensions if that isn't enough. Limiting the width yourself means it needs less quality reduction, and the letters stay cleaner.
5. Read the result line: the dimensions and the size before and after. If it says the result is larger than the original, your file was already small: keep the original.
6. Download it, open it and zoom in on the smallest text or detail before you upload it.

If you'd rather set exact dimensions first, for example a photo that must be 600 pixels wide, use the image resizer and then compress the result.

Keep the text on a document readable

A certificate, an ID card or a receipt is useless if the reviewer can't read it. Most of the work happens before you compress.

• Take a good photo. Put the page on a flat surface in daylight, hold the phone straight above it, don't use the flash (it causes glare), and let the page fill the frame.
• Crop the edges in your phone's photo editor: the table, your fingers and the background are pixels that cost space and add nothing.
• Don't shrink it too far. A letter or A4 page 1,300 pixels wide has about 150 pixels per inch, enough for normal printed text. Below about 1,000 pixels, small print starts to blur.
• Use a clean background. An evenly lit white page compresses much better than a grainy, shadowy one, so it keeps more quality at the same size.
• One page per file. If a document has several pages and the form allows several files, send one image per page instead of squeezing them into one.

JPEG or PNG for a scanned document?

For a photo of a paper document, use JPEG. PNG is lossless: it keeps every pixel exactly, including the paper's texture and every shadow, so the same photo in PNG can be many times heavier.

PNG works well for screenshots and documents made on a computer, which have flat areas of color. But the quality setting doesn't apply to PNG, so the only way the compressor can shrink one is by reducing its dimensions. If a PNG won't fit and the form accepts JPEG, choose JPEG in Format.

If the form asks for a PDF, compress the images first and then put them together with JPG to PDF. It adds JPEGs to the PDF without compressing them again, so the PDF weighs about as much as the images inside it.

iPhone photos in HEIC

By default, iPhones save photos in HEIC, a format that takes less space than JPEG. Many forms don't accept it, and Windows can't open it without an extra extension. If a file ends in .heic, or the compressor can't open it:

1. Convert it with HEIC to JPG. It also runs in your browser and removes the location and other hidden data from the copy.
2. Don't worry if the JPG is bigger than the HEIC: that's normal, because HEIC compresses better.
3. Compress the JPG as described above.

To make your iPhone save new photos as JPEG, go to Settings, Camera, Formats and choose Most Compatible. Apple explains the formats on its HEIF and HEVC support page.

Checklist

• I know the form's size limit, formats and any required dimensions.
• The photo is JPG, not HEIC or WebP.
• I set Max size a little under the limit.
• For a document, the width is about 1,300 pixels and the edges are cropped.
• I zoomed in on the result and can read the smallest text.

Frequently asked questions

Are my photos uploaded to eThorns?

No. The compressor, the resizer and the HEIC converter all work inside your browser. Your photos never leave your phone or computer.

My file says 98 KB, but the form says it's over 100 KB. Why?

Some websites count a kilobyte as 1,000 bytes and others as 1,024, and some add their own margin. Compress it again with a lower Max size, such as 90.

The form asks for exact dimensions, like 300 × 400 pixels. How do I do that?

Use the image resizer, type both numbers and turn off Keep proportions. You get the exact size, cropped from the center and never stretched. Check that nothing important was cut off, then compress it.

Can I get to 100 KB without losing any quality?

Not from a 4 MB photo. What you choose is where the loss goes: fewer pixels or less fine detail. For documents, fewer pixels with decent quality usually reads better.

Try it

• 3.2Compress imagesShrink JPEG, PNG and WebP images by quality, dimensions or a maximum size in KB, several at once.
• 3.4Resize imagesResize images by pixels or percentage, or change the aspect ratio (1:1, 4:5, 9:16…) by cropping or adding borders.
• 3.1HEIC to JPGConvert iPhone HEIC photos to JPG or PNG in your browser, several at once, with the JPG quality you choose.